When shipping lines began promoting slow steaming—operating ships at lower speeds to reduce fuel costs and carbon emissions—they highlighted its environmental benefits. Slow speeds reduce fuel consumption and, therefore, the output of harmful emissions, helping shippers reduce their carbon footprint and reinforce their green image.
Sailing ships at slower speeds does significantly reduce fuel consumption. Lowering engine speed by 10 percent cuts engine power by 27 percent, and reduces the overall energy needed for the voyage by 19 percent.
Shipping lines have widely implemented the slow steaming strategy of operating at 20 knots; some have even resorted to super-slow steaming at 15 knots. Slow steaming reduces shipping line costs, because it uses less fuel, and fuel comprises a huge share of operating costs. When oil prices were at their peak, fuel accounted for as much as 50 percent of the total cost of sailing a vessel.